Many procedures are known in the prior art for physically incorporating dying agents and other materials into polymer solids. Such methods and processes have for the most part failed to provide completely satisfactory solutions to the various technical problems involved, particularly in the incorporation of such chemicals as Prussian blue and other metallic complexes into polymeric systems. The present invention provides a simple yet highly effective chemical procedure whereby chemicals such as Prussian blue, or Prussian blue analogues, and constituting hydrated complexes of metal and cyanide ions, may be incorporated into and made reactive with a polymeric material such as polyacrylonitrile to produce a homogeneous, colored product exhibiting enhanced electrical properties correlated with the presence of the metal complex. One significant novel feature of the procedure of the invention is that it makes it possible to disperse or dissolve, at a much more uniform level, many substances which, heretofore, could not be so dispersed in a polymer solid. An important property of the resulting product is that the dispersion remains unchanged with time and is preserved even during subsequent dissolution of the polymer matrix.